mirror of
https://github.com/crazy-max/diun.git
synced 2024-12-23 03:48:00 +00:00
122 lines
3.4 KiB
Go
122 lines
3.4 KiB
Go
/*
|
|
*
|
|
* Copyright 2023 gRPC authors.
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*
|
|
*/
|
|
|
|
package grpcsync
|
|
|
|
import (
|
|
"context"
|
|
"sync"
|
|
)
|
|
|
|
// Subscriber represents an entity that is subscribed to messages published on
|
|
// a PubSub. It wraps the callback to be invoked by the PubSub when a new
|
|
// message is published.
|
|
type Subscriber interface {
|
|
// OnMessage is invoked when a new message is published. Implementations
|
|
// must not block in this method.
|
|
OnMessage(msg any)
|
|
}
|
|
|
|
// PubSub is a simple one-to-many publish-subscribe system that supports
|
|
// messages of arbitrary type. It guarantees that messages are delivered in
|
|
// the same order in which they were published.
|
|
//
|
|
// Publisher invokes the Publish() method to publish new messages, while
|
|
// subscribers interested in receiving these messages register a callback
|
|
// via the Subscribe() method.
|
|
//
|
|
// Once a PubSub is stopped, no more messages can be published, but any pending
|
|
// published messages will be delivered to the subscribers. Done may be used
|
|
// to determine when all published messages have been delivered.
|
|
type PubSub struct {
|
|
cs *CallbackSerializer
|
|
|
|
// Access to the below fields are guarded by this mutex.
|
|
mu sync.Mutex
|
|
msg any
|
|
subscribers map[Subscriber]bool
|
|
}
|
|
|
|
// NewPubSub returns a new PubSub instance. Users should cancel the
|
|
// provided context to shutdown the PubSub.
|
|
func NewPubSub(ctx context.Context) *PubSub {
|
|
return &PubSub{
|
|
cs: NewCallbackSerializer(ctx),
|
|
subscribers: map[Subscriber]bool{},
|
|
}
|
|
}
|
|
|
|
// Subscribe registers the provided Subscriber to the PubSub.
|
|
//
|
|
// If the PubSub contains a previously published message, the Subscriber's
|
|
// OnMessage() callback will be invoked asynchronously with the existing
|
|
// message to begin with, and subsequently for every newly published message.
|
|
//
|
|
// The caller is responsible for invoking the returned cancel function to
|
|
// unsubscribe itself from the PubSub.
|
|
func (ps *PubSub) Subscribe(sub Subscriber) (cancel func()) {
|
|
ps.mu.Lock()
|
|
defer ps.mu.Unlock()
|
|
|
|
ps.subscribers[sub] = true
|
|
|
|
if ps.msg != nil {
|
|
msg := ps.msg
|
|
ps.cs.TrySchedule(func(context.Context) {
|
|
ps.mu.Lock()
|
|
defer ps.mu.Unlock()
|
|
if !ps.subscribers[sub] {
|
|
return
|
|
}
|
|
sub.OnMessage(msg)
|
|
})
|
|
}
|
|
|
|
return func() {
|
|
ps.mu.Lock()
|
|
defer ps.mu.Unlock()
|
|
delete(ps.subscribers, sub)
|
|
}
|
|
}
|
|
|
|
// Publish publishes the provided message to the PubSub, and invokes
|
|
// callbacks registered by subscribers asynchronously.
|
|
func (ps *PubSub) Publish(msg any) {
|
|
ps.mu.Lock()
|
|
defer ps.mu.Unlock()
|
|
|
|
ps.msg = msg
|
|
for sub := range ps.subscribers {
|
|
s := sub
|
|
ps.cs.TrySchedule(func(context.Context) {
|
|
ps.mu.Lock()
|
|
defer ps.mu.Unlock()
|
|
if !ps.subscribers[s] {
|
|
return
|
|
}
|
|
s.OnMessage(msg)
|
|
})
|
|
}
|
|
}
|
|
|
|
// Done returns a channel that is closed after the context passed to NewPubSub
|
|
// is canceled and all updates have been sent to subscribers.
|
|
func (ps *PubSub) Done() <-chan struct{} {
|
|
return ps.cs.Done()
|
|
}
|